Sharp has developed a 5.5-inch display with 3860 x 2160 pixel resolution, which is equivalent to “ultra high definition,” also known as 4K.

The prototype LCD display, which could be used in smartphones in the future, has a pixel density of 806 pixels per inch (ppi) and was shown off last week at the China Information Technology Expo in Shenzhen, China. It was part of a larger, 12.5-inch IGZO panel.

Sharp hasn’t decided on a schedule for mass production yet. “Currently there are no driver ICs for small 4K panels, so the panel is not ready for mass production at this point,” Sharp spokeswoman Miyuki Nakayama said via email.

The company wants to develop and mass-produce 4K screens for clients’ phones but it’s too early to say whether they will be used in Sharp’s own Aquos line of smartphones, she added.

By comparison, Apple’s iPhone 6 Plus has a 5.5-inch screen with 1920 x 1080 pixel resolution and a density of 401 ppi.

Sharp regularly exhibits cutting-edge display technology, and first brought its high-definition IGZO displays to smartphones in 2013, introducing pixels that were smaller than those in conventional LCD screens. IGZO is named for the indium gallium zinc oxide semiconductor technology developed by Sharp.

The company, however, has been trying to reform its struggling LCD business amid fierce competition from rival manufacturers in China and South Korea. It is expected to announce the results of a review of its medium-term management plan next month.

Over the past year, Sharp has turned out thin-bezel, high-def displays for its Aquos Crystal smartphone, as well as prototype 70-inch capacitive LCD panels that are sensitive enough to respond to brushstrokes.